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Tuesday, June 28, 2016

By far the most prolific constituent of the fossils I found in the Martin formation in Arizona is Thamnopora sp. This genera is also called Coenites in older literature. It is most common as finger like branches covered in individual corallites, but also forms amorphous masses. Teichert mentions in his paper:

Among tabulate corals Thamnopora is by far the most commonly represented genus, and in many beds it occurs alone (fig. 26). Like Amphipora, the branches of Thamnopora colonies are seen in many outcrops on weathered surfaces, even on entirely dolomitized rocks. The habitat of the colonies is similar to that of the "Rasenriffe" (meadow or turf reefs) of German literature, which are not reefs but are horizontally extensive dense growths or thickets of branching corals, generally composed of one species. (See, for example, Hotz and others, 1955, p. 64, 76, 95.) Branching tabulate and phacelloid rugose corals formed this kind of biota in Devonian times in many parts of the world.

Here is a rock with lots of Thamnopora sp. branches emerging from it. Based on the size of the openings there may be more than one species present. There also appears to be a specimen of Disphyllum sp. present as well.

Here is a specimen that I etched out of the rock. It shows the amorphous mass like growth with branches that angle up.As I was photographing the specimen I noticed that there was a pattern near the base of the Thamnopora colony that looks like a Pachyphyllum corallum. You can see it in the second photo below and the last photo which is of the underside of the specimen. It appears that this Thamnopora colony either grew on an old Pachyphyllum colony or was living along side of it.

These specimens are from the Jerome member of the Martin formation (Devonian, Fransian stage) north of Payson, AZ.

Saturday, June 25, 2016

One of the more unusual looking pieces I found in the Martin formation of Arizona was a piece that resembles Alveolites sp. It is a flat topped piece with an epitheca on the underside and what appears to be a vertical growth element so that, in profile, it looks a little like a mushroom. The corallite openings on the dorsal surface are the most telling. They appear to be laying on their side and shaped a little like a fish scale. This is a diagnostic feature of Alveolites which is what leads me to believe my piece is of the same genus. The genera is listed by Teichert in his paper and illustrated in Langland's article.

Dorsal surface

Dorsal surface tilted and a little closer to show the corallite openings.

Profile

Ventral

This specimen is from the Jerome member of the Martin formation (Devonian, Fransian stage) north of Payson, AZ.

Thursday, June 23, 2016

I found one pebble of limestone from the Martin formation in Arizona that was shot through with a narrow, stick like coral that I believe is Syringopora sp. The genera is listed by Teichert in his paper and is illustrated by Langland in his article. The calices are very narrow, 3-5mm across and clustered but not in a central mass. Think of them more as loose spaghetti. My sample is small and there is not much exposed of the sides of individual calices, so could this possibly be a form of Aulocystis?

This specimen is from the Jerome member of the Martin formation (Devonian, Fransian stage) north of Payson, AZ.

Monday, June 20, 2016

These next two specimens represent a new (to me) genera: Disphyllum. They are a colonial rugose coral with closely set, yet independent calices. It looks similar to Eridophyllum but the calices are shorter. Both specimens that are shown here are small clusters. I don't know if they form larger colonies or is these represent the typical form.

I looked through Stumm's paper and did not find any mention of Disphyllum. I based my ID of these fossils on Langland's article in Rocks and Minerals where they illustrate two species but do not list specific names. Teichert's paper does list several species of Disphyllum.

Specimen #1 - Dorsal view

Dorsal view rotated 90 degrees

Right profile

Left profile

Specimen #2 - Dorsal surface

The next four pictures are the specimen in profile view, rotated 90 degrees in each subsequent photo.

These specimens are from the Jerome member of the Martin formation (Devonian, Fransian stage) north of Payson, AZ.

Saturday, June 18, 2016

One of the most mysterious fossils that I found in the Martin formation of Arizona is this large chuck of silicified rock. The softball sized piece is composed entirely of a single colony of some sort of coral or bryozoan. As you can see in the pictures below, it is a very three dimensional piece with "pores" on all side and every surface. The small openings vary in shape but do show some "flowing" features that I interpret as a growth pattern. I don't think this is the coral Alveolites as the corallite openings of that genera are flattened and resemble fish scales. It's not likely a sponge due to the many small openings and growth patterns which sponges or stromatoporoids do not possess. I'm thinking that this is part of a massive Bryozoan colony of some species in the Family Fistuliporidae. I have found similar large and massive colonial structures like this one from the Hungry Hollow mbr. of the Widder formation from Hungry Hollow, Ontario.

Closer views of the small openings.

These specimens are from the Jerome member of the Martin formation (Devonian, Fransian stage) north of Payson, AZ.

Wednesday, June 15, 2016

Some of the silicified coral fossils that I found in the Martin formation of Arizona were composed of many small tubes that clustered close together. I recognized this as a form of Aulopora which is an encrusting type coral which sometimes forms clusters or chains on the surface of brachiopods, corals or any other hard surface. The coral colony expands by clonal budding with the new polyp attached to the exterior of it's progenitor. Aulopora is always a neat coral to find as it often forms interesting patterns or shapes on whatever surface it encrusts. Jeffery and Edith Langland do include a picture of an Aulopora specimen in their article (see reference below) that looks similar to the first specimen below.

Specimen #1 is a large, flat encrustation that appears to have colonized an overturned coral colony

Specimen #2 appears to be less of an encrustation and more of a vertical aspect where the polyps are using the bodies of their neighbors as a support. To me this growth habit is more reminiscent of the genera Aulocystis.

Specimen #3 has a similar growth pattern

These specimens are from the Jerome member of the Martin formation (Devonian, Fransian stage) north of Payson, AZ.

Friday, June 10, 2016

I found a few specimens of a colonial rugose coral with some really deep corallites in the Martin formation north of Payson, AZ. At first I thought they might be Hexagonaria sp. but the cup depth is much greater than that genera. So, after researching a bit more, I think I have Spongophyllum sp. specimens. Here is the description for the genera that Ermin C. Stumm wrote in his paper "Upper Devonian Compound Tetracorals from the Martin Limestone", Journal of Paleontology, Vol. 22, No. 1 (Jan., 1948), pp. 40-47:

Phaceloid, subcerioid, and ceriod corals composed of cylindrical, subpolygonal, or polygonal corallites. Septa of two orders, major and minor of which the former are of variable length and the latter short or lacking. The septa are thin and are separated from the peripheral wall by a small, irregularly developed lonsdaleioid dissepimentarium. The tabularium is composed of tabulae that are usually large and complete. The peripheral dissepimentarium is composed of a single row of vertically disposed, elongated dissepiments. The dissepiments may overlap or double up in certain areas and may be discontinuous in others.

I'll be honest, I have no idea what much of that means. After doing a bunch research with dictionaries, and Google.com, this is how I translate that description:

Individual corrallites are round to slightly polygon shaped and can be columnar with slight separation or joined together with common walls. Vertical septa lines vary in length with occasional smaller lines between. The septa are thin and separated from the outer wall by small, irregularly developed, blister like skeletal walls. The colony is composed of corallites that are usually large and complete. The outer wall is composed of a single row of vertically arranged, elongated skeletal walls. The skeletal walls may overlap or double up in certain areas and may be discontinuous in others.

Hopefully that makes a bit more sense. Stumm lists two species of Spongophyllum in his paper: S. martinense and S. breviseptatum. The main difference between the two appears to be the length of the septum as measured from the outer wall. The length is 1mm in S. martinense and .5mm in S. breviseptatum. Now, onto the fossils!

Specimen #1 - dorsal view

Profile of the broken side - (it appears at first glance that the internal skeletal structure may not have been preserved and instead these fossils are steinkerns)

Ventral view

Profile of the unbroken (edge of the colony) side

Isometric view into the corallites where you can see the septa (thin vertical lines)

Specimen #2 - dorsal view

Same view, just rotated 90 degrees. The rest of the fossil was not terribly photogenic.

These specimens are from the Jerome member of the Martin formation (Devonian, Fransian stage) north of Payson, AZ.

In addition to Google.com and the dictionary, I used the following references to identify these specimens:

- A helpful powerpoint with coral anatomical terms and examples from Dave Krupp's website.
- The website Corallosphere.org where I was able to figure out some of the technical terms that Stumm used in his descriptions.
- Langland, Jeffrey O. and Edith V., 2012, "Fauna of a 400-Million-Year-Old Coral Reef in
Arizona", Rocks and Minerals, 87:1, 40-44

Saturday, June 4, 2016

One of the most common fossil corals that I found from the Martin formation is Pachyphyllum nevadense. Trying to get a nice big piece was hard as the fossils break off as they weather out of the rock. Pachyphyllum is a colonial rugose coral that is easy to recognize by the many circular corallites that are surrounded by linear striations. The lines are the septae of the coral which means that the body of the animal would have extended out of the cup shaped, round depressions until it met a neighbor. As colonial corals of all kinds are clonal by nature, this would not have been an issue between members of the colony, only if it met a different colony.

This is a small, complete colony which shows some vertical growth. Perhaps this indicates that it had to compete with other surrounding colonies for space or needed to outgrow the deposition of sediment around it's base.

Here is a larger colony which appears to have been later colonized by a stromatoporoid (along the edge of the piece at the top of the picture).

Lastly is this nicely preserved, but partial colony.

A side view of the colony where you can see the generally wide and flat growth pattern.

This is the underside of the specimen. It appears to have either not been fully preserved or perhaps was exposed and reworked on the ocean floor before final burial.

All the fossils shown on the page have been silicified (replaced by quartz). This process can sometimes be imperfect and that is why there are often gaping holes or seemingly incomplete preservation. These specimens are from the Jerome member of the Martin formation (Devonian, Fransian stage) north of Payson, AZ.

About Me

I'm a 40-something, life long student of Geology living in Philadelphia. My interests include Photography, Architecture and History among other things. When not cleaning my recent finds you'll find me in my backyard Hybridizing Daylilies or working in my garden. This Blog is an outlet for me to express my interest in fossils, catalog my collection and coalesce my thoughts and research into a useful medium.